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IMAX/Large Format Film/IMAX technical specifications

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Question
Hello there, my name is Simon and I'm from the UK. I'm autistic and I have many personal interests, and filmmaking has recently become one of them. I have some questions regarding the IMAX format, even though I know comparatively little about the industry and my understanding of the correct terminology is limited, but I shall try my best. I am curious, why are the dimensions of the IMAX format so boxy? It almost looks like the 4:3 aspect ratio of old school television sets. Wouldn't it make more sense for the frame to be closer to the 1:85:1 aspect ratio? I must inform you that my mind is working on the assumption that aspect ratio and frame dimensions are the same thing. Please correct me if I'm wrong.

Another query I have is, instead of having 15 perforations per frame, why not simply increase the size of the perforations relative to the size of the format?

I may ask some follow up questions if you are able to help. Thank you.

Answer
Why are the dimensions of the IMAX format so boxy?
Sitting in the IMAX theatre you are looking out a huge window, action is happening all around the screen.  You have to look left, right, up, down.  Hence the boxy shape.  In a practical construction sense, you are constrained, generally, by the horizontal dimension or the vertical dimension.  So if constrained, maximize the other dimension.

Secondly, IMAX is recorded on 65mm film, 1:85 would only use a portion of the film negative.  The film frame is fully filled with content without loss when projected on the IMAX screen.

Basically in a production sense, aspect ratio and frame dimensions are the same thing.  We use the terms generally interchangeably.

Perforations in film are where the teeth of the camera gears engage the film to move it along its path.  Perfs are minimized as much as practical to increase recorded content within the frame.

IMAX/Large Format Film

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Michael Cook

Expertise

Production - how they get made History - where it all began and who the players were/are. What I cannot answer is where the money comes from as that is a never ending quest. Generally, I seek financing from corporate sponsors and people and organizations with an affinity for the subject.

Experience

I have been working in the large format film arena on the production side for nearly 30-years. I produced the large format film "The Greatest Places" in current release at IMAX and other giant screen theaters. And on DVD.

Organizations
Giant Screen Cinema Association - the chief industry organization

Publications
numerous

Education/Credentials
BFA from New York University (NY NY), in film production

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